The social networking arms race has gone global. A recent report from online metrics firm comScore (NASDAQ: SCOR) revealed that social networking sites such as Facebook, MySpace, Orkut, Bebo and Hi5 have collectively seen their traffic rise by 25 percent over the last year.

Of course, the popularity contest is usually dominated by talk of Facebook vs. MySpace. In April, Facebook overtook MySpace to become the world's largest social network. The new report shows that Facebook posted 153 percent growth in unique visitors from June 2007 to June 2008. In that same period, MySpace grew just 3 percent.

comScore credits much of Facebook's global surge to its translation applications, which has enabled more than 15 foreign-language versions of the site.

The news serves as but the latest reminder of the importance of global audiences to online media brands -- particularly as North American advertising revenues and user growth slow.

Overall social networking growth in North America, up just 9 percent from June 2007 to June 2008, appears to be leveling off. In emerging markets, however, traffic to the social sites is still increasing rapidly. The number of unique visitors to social networks in Africa and the Middle East increased 66 percent, comScore found.

"While the social networking trend first took off in North America, it is beginning to reach a point of maturity in the region," Jack Flanagan, comScore executive vice president, said in a statement. "However, the phenomenon is still growing rapidly in other regions around the world -- especially as the established American brands turn their focus to developing markets."

The second-biggest gainer was Hi5, which saw its global reach double to more than 56,000, a jump which comScore attributes to its localization strategy. Also posting impressive gains in global reach were the social networks Friendster (50 percent), Orkut (41 percent) and Bebo (32 percent).

Despite its near-flat global growth, MySpace, which still has the largest U.S. audience, says it is succeeding where it counts: engagement.

Citing comScore data, MySpace boasts that its users spent 20 percent more time on its site this June than a year earlier, giving it a nearly threefold edge over Facebook in terms of time spent on the site.

More time spent on the site, of course, equate to more ad impressions, a crucial metric for social networking sites, which are still struggling to figure out how to monetize their content. Engagement was the watchword of AOL's hype surrounding its $850 million acquisition of Bebo earlier this year.